If you don't know should you be doing it? It's a free country I know but if you don't know how then even if you get the reading will you know what to do with them? Seems a big expense to buy the test equipment when you could have someone in to do it for you.

If you want to carry out a simple check on combustion performance. run the boiler at full rate for 2 minutes and time your meter or if it is a dial type you can record the time to take one revolution. Then you can perform a calculation to determine how much gas was consumed and the output of the boiler that consumed it. It should be close to the data plate heat output.

Perhaps someone more familiar with US gas meters could help you further.

Clocking the gas meter and determining input matches rating plate is far from combustion testing. This process at best may help you determine if manifold gas pressure is near correct, but not perfect without a true manometer.

For sure you can do all that and more with a combustion test but what good is it if you don't know what to do with the readings.

You could also if you can view the flame picture and tell its colour shape whether it is lifting off the manifold or not, if it is a premix burner you could check the colour only (if you can view it). But again all this presupposes the user knows what to look for.

But the test I suggested doesn't require the user to touch the gas controls in anyway and is a check of the performance of the appliance that can help the user find a simple problem. You could have the correct gas pressure from the gas valve to the manifold and still have a poor flame picture leading to incomplete combustion, which would show up on a gas rate test I suggested. Further Premix burners there is no means to check manifold pressure because of the nature of the design.

Regarding pre-mix positive pressure gas valves on the Triangle Tube Prestige series boilers, they have a tech supplement for adjusting manifold gas pressures.

Navien tankless water heaters who happen to be positive pressure gas valves, and to my best knowledge, the only tankless with pre-mix burner (all others being lean-rich), have adjustable manifold pressures.

I understand that in Europe, for instance when installing a Viessmann for example they state set gas regulator for 21 bar, well here we don't always have the luxury of setting incoming gas pressure so that our mix is correct based on factory settings, thus we tune the gas valves for a proper install.

I understand that in Europe, for instance when installing a Viessmann for example they state set gas regulator for 21 bar, well here we don't always have the luxury of setting incoming gas pressure so that our mix is correct based on factory settings, thus we tune the gas valves for a proper install.

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it wouldn't be 21 bar it is 21 mBar and that figure refers to the regulator on the gas supply meter into the house. We're allowed no more than a 1mb drop from gas inlet pressure to the boiler from the outlet of the meter.
So if the regulator is set to 21mB then the supply to the boiler inlet pressure can be no less than 20mB at max working boiler load.

This has nothing to do with the Premix burner which I'll repeat has no means of recording the gas outlet pressure only the supply side to the gas valve.
It's not what I read on the internet it is the gas regs and manufacturer information and knowledge here. But I'll read up the boilers you mention as certainly the Viessmann boiler would be the same here as in the US.

DO NOT ATTEMPT TO MEASURE VALVE OUTLET
PRESSURE The valve could be damaged by manom-
eter fluid contamination. Failure to comply could result
in severe personal injury, death or substantial property
damage.

That's from the WeilMcLain Ultra3 manual, it's repeated several times show me the manifoldgas pressure for that boiler. Incidentally we're off topic now way off topic but it supports my assertion that what's the point measuring something if you don't know what it is you're measuring.

That burner they use looks suspiciously familiar like a remaha quinta 45 I work on every year I have to replace the electrodes and gaskets seals and clean out the aluminium corrosion. its horrendous at condensation eating it all away, the client knows it needs doing as it lights with a bang, when the electrode is 60% eaten away. Me thinks these two are the same. This boiler is continuously in condensing mode as it heats his pool. so instead of a 12 month service it is done every 6 months. I'll have to dig some more.

Check gas valve outlet pressure
After following the start-up procedures of manual Section
VII, follow the procedures of Section VIIf to measure gas
valve outlet pressure and adjust if necessary.
Failure to check gas valve outlet pressure and adjust, if
necessary, could result in severe personal injury, death or substantial
property damage. Carefully follow the guidelines given in this manual.

Why do you challenge a US boiler guy on US boilers?

I believe I stated earlier that this is not for all tech's to know and understand. The general install manual doesn't always include the advanced service and set up info

Check gas valve outlet pressure
After following the start-up procedures of manual Section
VII, follow the procedures of Section VIIf to measure gas
valve outlet pressure and adjust if necessary.
Failure to check gas valve outlet pressure and adjust, if
necessary, could result in severe personal injury, death or substantial
property damage. Carefully follow the guidelines given in this manual.

Why do you challenge a US boiler guy on US boilers?

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So please send me a copy of the manual you refer to or a link to get it myself. I may be disagreeing with you, but I'm not getting upset about it and it certainly has nothing to do with politics.

We're also talking about "both easily set up with a manometer for correct firing rates. " and clearly it's not if it is not in the manual supplied with the boiler in the instance I have cited (http://www.weil-mclain.com/downloads/ug3_boiler_manual.pdf), that a DIY person would be recommended following which is how this topic first came about for DIY use.